Since its original publication in 1980, The Art of Electronics has been regarded as a masterpiece of electronic engineering. Engineers have hailed it as an indispensable, life-altering work which has greatly deepened their understanding and love of circuit design. The highly-anticipated third edition was released earlier this year and has already garnered rave reviews. element14's Sagar Jethani spoke with co-authors Paul Horowitz and Winfield Hill about the new third edition.

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Art of Electronics co-authors Paul Horowitz (L) and Winfield Hill (R)

element14 member Don Bertke, asks: Why The Art of Electronics? Isn’t electronics a codified discipline? Art implies a degree of imprecision or subjectivity.

Horowitz: It was Win’s idea to call it “The Art of Electronics.” I think we said it right in the first edition: electronic circuit design is an art. It’s a combination of some basic laws, some rules of thumb, and a large bag of tricks. In our opinion, a good circuit design also has elegance. There’s a beauty to it when you’ve done it in a nice way that combines a good choice of components demonstrating a clever use of their properties in a robust and reliable design that does what you want.

The ability to practice this art really grows the more you do it. It takes many years before you can see through to a beautiful design.

Hill: You can learn it by doing, but we think if you read enough stories, little examples of how the art is crafted, then you can get a good way along and become a better designer without having spent so many years of practice to get there.

Horowitz: You can take a microcontroller and you can program it to do something, but there are probably numerous ways to do it better, cheaper, and at lower power—and in a way that is very emotionally satisfying if you take the time to learn the art of circuit design. So we stand by our title.

What’s different about the new third edition? Is it a complete rewrite, or an incremental update?

Hill: The first couple of chapters are expanded and rewritten, but many of the rest of them are virtually written from scratch. Topics such as filters, oscillators and timers, switchmode power converters, transmission lines, TV, and microcontrollers include substantially new material, as do our greatly expanded treatments of MOSFETs, logic families and interfacing, serial buses, A/D conversion, optoelectronics, transimpedance amplifiers, and low-noise and precision design.

Horowitz: Originally, the first edition came from a course we were teaching, and we thought of it as an enhanced textbook. We soon discovered that most of our readership was comprised of professional engineers. For that reason, we really bulked-up the third edition with some seriously grown-up topics. A lot of these are on the periphery of microcontrollers.

Embedded controllers have become so common, so we’ve added the sort of analog subjects that have become very important because they surround the microcontroller core. Things like precision design, so we have a rather extensive and fully re-written chapter on that, low-noise design, power switching and power conversion, and analog-to-digital and digital-to-analog conversion. Those four chapters are really something. Each one of them could really be its own small book. And we’ve added a bunch of new topics that were not in the previous editions that we felt were of interest to professional designers more so than for someone taking a course in electronic circuits.

Hill: We added 50 photographs to the book. They’re nicely annotated, and really show what things look like. We’re quite proud of these photographs, and we spent a lot of time making them. I think it’s a feature that really improved upon the second edition, largely because of the ability to now use digital photography to make them look beautiful. And our publisher chose a very smooth-surfaced paper to retain the high quality of these photographs.

One of our members, Erik Ratcliff, asks if he hasn’t already purchased any of the editions, which one should he start with? Can you describe more of the content he will find in the new third edition which isn’t in the second edition?

Hill: We believe that everyone should have a copy of the second edition. There’s a lot of great material in the second edition that we dropped the chapters wholesale, and there are other cases where we rewrote chapters entirely for the third edition. A lot of people were not interested in just getting a warmed-over update of the second edition—they wanted to see brand new stuff, and Paul and I really wanted to write new stuff.

Horowitz: Another new aspect of the third edition goes back to the illustrations, especially scope readouts. This is something that was made possible by the digitization of oscilloscopes which occurred between the publication of the second and third editions. In the old days when you had an analog scope, you could only photograph the screen and it would become a halftone photograph in the first and second editions of the book. But with digital scopes, you can now make nice line art. We’ve got 90 scope shots in the third edition which show the authentic behavior of circuits, compared with maybe five in the second edition.

Hill: When you have the electronic version of a scope screen, you can edit it, and even superimpose and put multiple scope screens together. You can create scopes that have more channels and traces than your hardware will actually allow.

Horowitz: Yes, I have some six or eight channel scopes displayed in the third edition.

Win, you mentioned that some topics from the second edition were dropped altogether for the third edition. Can you give some examples?

Hill: “Good circuits, bad circuits” is gone, but will soon reappear on the Art of Electronics website. We’ve also removed the construction chapter, the low power chapter, and the scientific instrumentation chapters. Somebody might want to have this content, and that can be found in the second edition.

Horowitz: We did incorporate some of that material into different chapters of the third edition, but it’s true that those specific chapters are gone.

Throughout the text, you refer to x-chapters. element14 member Shabaz Yousaf asks if you can explain what these are.

Horowitz: For someone starting to read this book without much background in electronics, we wanted to provide them with a basic introduction to circuit design. But for the real experienced reader, we wanted to go a layer deeper and get into the difficult problems and really push into the edge of the envelope. So we decided we would put this into extra chapters we call x-chapters. They will follow some of these more basic chapters.

Our original objective was to put each of these right after each chapter that it attaches to in the book. As it happened, the third edition got up to 1,200 pages even without the x chapters—even with larger pages and a somewhat smaller font. So about a year ago we made the decision to publish the x chapters as a separate book. We took some of the material that we had intended to put in the x chapters that we felt was really important and we put it back into the main text of the third edition. So some of the chapters now in the main book are more sophisticated.

When do you plan to release the x chapters?

Horowitz: The x chapters book will come out in no more than two years’ time—I would like it to be less. It’s already about fifty percent written with figures and everything else already.

My next question comes from element14 member John Wiltrout. The second edition has a popular student manual. Are you planning to release something similar for the third edition?

Horowitz: The third edition goes a little more toward the professional designer, so we have taken some of the more basic material and enhanced it into what used to be called the student manual. It’s now going to be called “Learning the Art of Electronics: A Hands-on Approach.” We used to call it the little book, but that “little book” is now about a thousand pages! It’s quite substantial. It incorporates the labs and the classes and all that stuff that’s in the current student manual, plus some additional stuff. It takes some of that basic load off the main volume. It’s written by Tom Hayes, the first author of the previously-released Student Manual.

The Maker movement has grown significantly since the second edition was published. It sounds like the Learning the Art of Electronics (the student manual) will cater to those who have more of a hands-on learning style, as opposed to those who prefer to learn from a traditional text.

Horowitz: Yes, I think so. The student manual covers the electronic labs we’re using here at Harvard, and it’s a set of lessons that you build with your hands.

But I would also say that the main Art of Electronics text is not a traditional text in any sense of the word. A traditional text in some sense can be both too mathematical and kind of boring. On the other hand, I find a lot of multimedia, like watching a video blog on how to design stuff, too slow! I want to move more quickly. I think you can move through our book at your own speed. It’s full of circuits that you can build, and it’s full of what the waveforms look like.

It’s really designed to get you doing hands-on work.

Hill: Yeah, it’s all rubber-meets-the-road kind of stuff. That adds to the practical aspect that’s in the book. You can’t get that kind of stuff on the Web. I love looking at blogs, but after looking at them for half an hour, how much have you really learned? We go into things a lot more deeply in the book. It’s hard for me to see how a format other than the printed page is really suitable for that kind of serious material that we have.

element14 contributor Elecia White was curious to know if, given the depth of your book—90 oscilloscope shots, 80 tables, over 1600 components—you have some favorite circuits? Some that you find yourselves constantly going back to as points of reference?

Horowitz: I find this a very interesting question. We have a favorite graph, and it’s on page 526. In one graph, it basically has everything you need to know to do a low-noise op-amp circuit. It’s just an incredible picture. It’s got all the parts, it’s got all the curves, and it’s got everything you need to know. Even a little tutorial with a graph marking some equations on it. Also, I had a lot of fun building figure 8.58 in Adobe Illustrator. It’s about Effective Input Noise Density, and it took everything I knew about Illustrator to make that happen. That’s our favorite graph.

Any favorite tables?

Horowitz: Our favorite table is table 5.5 which supposedly covers “seven” precision op-amps—but it actually has about seventy five! It has pretty much all the op-amp parameters you need to know to choose one, made in conjunction with that graph we just talked about. There’s a lot of information you’ll find in there that you actually won’t find in datasheets.

For instance, the LT1012, which is a bias-compensated bipolar amplifier, has a completely incorrect specification on its datasheet for input current noise because they didn’t take into account the fact that if you cancel one current with another uncorrelated current it doesn’t subtract the noise—it actually adds to the noise power. So they have specs that are off by an order of magnitude or more. That sort of stuff is in that table as well as in the text.

We actually had a nice chat with Jim Williams on that one. We pointed out that this LT1012 spec was completely bogus. There was this long pause at the other end, and then in a low tone, he said, “You’ve uncovered one of the dark secrets of Silicon Valley.” (laughs)

You’ve given me your favorite graph and your favorite table. Do you have a favorite circuits?

Hill: I’m not sure we have any one favorite circuit, but we can list a few.

Horowitz: We had a lot of fun thinking about this one. Throughout the book, we decided we’d take some example circuits and present them in different ways because a lot of the art of engineering is about making choices. You choose this version or that, maybe because of price, performance, or some other factor. There’s no single “best” op-amp, for example.

One example we did was the sun tan monitor. It’s not something anybody really needs, but we thought it was kind of cute. We start back in the analog chapter talking about how you make an integrator to keep track of how much sun you’re getting. Then we go into the digital chapter and we have counters running it, then eventually we get into microcontrollers and they’re running your entire sun tan experience.

We did a similar thing for pseudorandom bit sequence noise generators. We go from discrete digital logic through to FPGA, CPLDs and then, ultimately, microcontrollers. We actually spent 12 pages carrying you through half a dozen different ways you can make a pseudorandom sequence. We have a nice example in figure 8.93 on page 559 which shows how to use a pseudorandom bit sequence noise generator plus analog filtering to make yourself three different colors of noise: white, pink, and red, including performance graphs for that circuit.

By the way, when we put a circuit in, we name names. So you’ll see the part numbers, you’ll even see the pin numbers. In most cases, we actually built these circuits, so you’ll also see the performance as well.

We thought that those circuits make a kind of nice sequence.

Hill: My favorite circuits include Figure 9.13 on page 606. It shows the internal circuitry of the 317-style linear regulator. I’ve always thought that was especially elegant and cute. These are circuits that we put in the book that other people designed, and some of them are very nice. I really love the HP/Agilent/Keysight DMM circuitry which we cover in number of places in the book, like Figure 849 on page 513, Figure 1315 on page 896, and Figure 1347 on page 919. These are different aspects of the instrument which are covered in the book.

A lot of disruptive innovations have taken place in the world of electronic engineering since the second edition was published in 1989. You have been in a unique position to observe these changes as they unfolded. Is there a specific technology that either of you feel will fundamentally alter the nature of electronic design in the next twenty years?

Horowitz: When we were kids, if you wanted to do electronics, you were into ham radio. If you wanted to do automobiles, you took your car apart. We went from that into an era in which nobody did anything because they just bought packaged stuff. Now we’re back to an era in which people are making stuff again, and we’re very pleased to see that. Of course, part of that is due to the availability of inexpensive microcontrollers and little prefab platforms like Arduino and Raspberry Pi and so on.

But I think a bigger part is the Internet. It’s really the ability to find out with just a few keystrokes what other people are doing. And to share your ideas and to get the answers to just about any question by asking it in online communities that has really made this whole movement take off. So if we’re going to ask what’s been disruptive, I think it’s been the Internet and the availability of inexpensive components.

As for the future, I’m chastened by Niels Bohr’s comment in which he said, “Prediction is very difficult, especially if it's about the future.”

Hill: The last edition of the book was in 1989. If somebody had asked us what was going to change in 25 years…

Horowitz: I don’t think we would have foreseen Arduino, the Internet, Make Magazine and all that. I would have said in the 1960s that tunnel diodes were going to be the big thing! They were going to blow away transistors—they were fast, they were simple, they were cheap. Where did they go? They’re pretty much gone. So I think anybody who predicts is a fool.

Hill: We’re dodging that question!

You’ve mentioned the impact of microcontrollers a few times. At element14, we sell a wide variety of MCUs. Shabaz and I were recently discussing whether the introduction of such fully-featured, low-cost boards have changed the nature of design. Is there any downside? In the old days, an engineer might have sat down and actually come up with a really elegant circuit that serves the needs of the application. But today they just don’t have the time. So instead they’ll reach for a microcontroller that they’re already familiar with to get the job done. It may be a little overkill, but it will suffice.

Horowitz: My cautionary comment, if there is one, is that in some sense you’re sticking these microcontrollers together like LEGOs and oftentimes you can get a circuit to work. But if you really want to push the envelope on what you can do, chances are this approach is suboptimal. At some point you really have to bear down into the difficult parts.

Let me give you an example of what happens here at Harvard. We have students who get a design problem: build such-and-such. They go out to popular websites, grab a bunch of modules, and they snap them together, hoping it’s going to work because, you know—it looks like this output goes into this input. And it doesn’t work. The problem is that they don’t really understand problems like different voltage levels, or impedance levels, or bypassing. They end up with stuff that either blows up or just doesn’t work very well. Or it’s oscillating but they just don’t know it because they’re only looking at what’s on the screen and not on a real oscilloscope. I guess I worry that by having these snap-together things, you sometimes miss the important stuff that’s really essential for reliability and for meeting performance standards that matter.

On the other hand, if it gets the job done, who’s to complain if it works for you? I’m pleased that these microcontroller are basically now just components, and that they’re part of people’s designs.

Hill: Let me draw your attention to chapter 12 of our book: Logic Interfacing. This is where we teach how to interface processors to all kinds of things. Most of the world does not run on 3.3 volts, so how are you going to connect your processor pins to all the various kinds of things you’re after? This is what we talk about at length in chapter 12. Then in chapter 13 we discuss analog connections to those processors.

When you go and get your little board from TI or whoever, it has some pins that you can connect to other circuitry, but the serious question is: what will that other circuitry be?

That’s what we try to teach.

Too many people feel that if they learn their microcontroller, then they’re all set. But they come up short when they have to drive a big solenoid or something serious like that. Chapter 15 is our controller chapter, and we have three full-page figures on pages 1080, 1083 and 1085 which show different things hooked up to your processor. It’s quite inspiring to look at all the strange little things that are in here: stepping motor controllers, capacitance position sensors, video decoders, Ethernet—there’s just a whole mess of stuff that you would want to hook up. We spent a lot of time teaching people about the kinds of things they can do with that, too.

How can engineers keep their skills sharp?

Hill: You might have a processor that you know perfectly well, but maybe you’re curious about trying some new things. We think that’s great. That’s the best way to keep yourself sharp.

Horowitz: I spoke with our really skilled circuit designer, Jim McArthur, about this. We quote him a number of times throughout the book. He had a good comment: “In the end, you probably need Breakfast Club—people that you talk to who you really trust in terms of electronics and they tell you which things that you really need to be aware of.” If you have a small group of Breakfast Club people you can stay abreast without it overwhelming you and keeping you from getting the job done.

I notice you mentioned Newark Electronics in the appendices to the third edition.

Hill: I’m a regular buyer at Newark Electronics.

Horowitz: In Appendix K, “Where do I go to buy electronic goodies?” we specifically mention Newark as having a good selection of tools. I also say “Hooray!” because Newark still has a catalog in print, whereas Digi-Key gave it up a couple years ago.

Do you think we will have any new components in the next few years that we will come to see as being as indispensible as resistors, capacitors, and transistors are today?

Horowitz: I’m not investing in memristors yet. It will be interesting to see what the real nonvolatile memory technology will be. I don’t think it’s going to be floating-gate flash in the long run. I think there will be something much better, but I’m not sure which of the three or four contenders right now it will be—or if it will be something completely different. In the book, we stated the plusses and minuses of MRAM, FeRAM, phase-change memory, and so on.

Check with us in thirty years and we’ll see where it goes!

Paul, you are one of the pioneers of the SETI movement. You worked with the late Carl Sagan in advancing the search for extra-terrestrial intelligence. Could you describe your work here, and where SETI stands today?

Horowitz: SETI is alive and well. It’s a big space out there, of frequencies and directions and everything else. We don’t know what extra-terrestrial civilizations are sending, but we’re pretty sure they exist. If you had asked someone twenty years ago how many planets exist beyond our solar system, they’d have said probably not many. But if you ask someone today they would say there are more planets out there than stars.

There are more planets in the Milky Way than there are stars. And there are probably as many habitable planets in the Milky Way as there are stars—say 100 billion, plus or minus. Things are looking good for life elsewhere. In fact, things aren’t even looking so bad for primitive life elsewhere in our own solar system.

What’s the best way to communicate with other intelligent life in the universe?

Horowitz: Recent ideas are to look for optical pulses. That’s been our big thing for the last ten years, but radio is probably still the best bet. There’s not much going on in radio these days. The Allen telescope array, which was going to be the Great White Hope, has not worked out. Arecibo only has a very tiny pencil beam looking at the sky at a narrow range of frequencies—that’s SETI @Home.

Contact is going to happen one of these days, but what we’re doing so far is just scratching the surface. So far, unless it’s been classified, no one’s found a signal from an extra-terrestrial intelligence.

Hill: Paul and his students designed a telescope in Harvard, Massachusetts. It runs automatically when it’s a clear night, and it scans the night sky looking for life signals. He has not updated his web page for it because he’s been working too hard on the third edition of the book. (laughs) The telescope will be running tonight, right?

Horowitz: Well, it’s looking a little cloudy. We should be in California where you are, Sagar! (laughs)

Let me close this subject with a little quote. It’s from when were doing a radio experiments and upgrading the telescope Win just mentioned. I showed the upgrade to one of my colleagues, Bill Press, the author of Numerical Recipes. Bill looked at this thing and he said, “Horowitz, you know you have one chance in a million… of becoming the most famous person ever.” So, it’s a long shot.

But it would be a remarkable discovery. It would be the end of earth’s cultural isolation. It would be a bridge across four billion years of independent origin of life. It would be the greatest discovery in the history of humankind.

Hope springs eternal in this business.

Hill: So it will either be the greatest discovery in the history of humankind or nothing.

Horowitz: Or nothing. (laughs)

I want to give it to you both for producing what one of our members has called the holy scripture of electronic engineering. Congratulations on the amazing new edition.

Hill: Thank you very much. We enjoyed speaking with you.

Horowitz: If your member is right, does that make us saints? Or something more?

She didn’t clarify! (laughs)

You can purchase the new third edition of The Art of Electronics at Paul and Win's official site.